Woodside Petroleum Ltd.'s decision not to drag fresh impairments into its dividend calculation is good news for yield-hunting investors. It may also make the timing ripe for Royal Dutch Shell PLC to exit its investment in Australia’s second-biggest oil and gas producer.

Woodside this week guided investors to expect impairments for fiscal 2013 of up to US$400 million, which includes adjustments for the carrying values of certain projects and the amortization of other assets.

While that figure is considerably higher than the US$218 million that analysts at UBS had anticipated, they reckon Woodside’s decision not to include the impairments in its dividend calculation gives it the headroom to increase the final payout by 15 cents a share.

According to UBS analysts Nik Burns and Cameron Hardie, that should mean a second-half dividend of US$1.16 a share and a full-year dividend yield of 5.8% rising to 6.8% for 2014. On top of that, there should be plenty of investor appetite for a stock generating this sort of yield over the next few years.

And that may entice Shell to sell its 23.1% stake.

Shell has previously said it isn’t a long-term investor in Woodside. Messrs. Burns and Hardie think the timetable for a sale will be driven by price or a need to use the funds elsewhere.

Shell has loomed large over Woodside’s share register since its hostile 10 billion Australian dollar (US$8.8 billion) bid for the two-thirds of the Australian company it didn’t already own was rejected by Australian lawmakers in 2001 on national-interest grounds. Speculation that Shell wanted out heightened in late 2011 when it sold a 10% interest in the Perth-based company for about US$3.3 billion.

“Our view is that Shell should take the opportunity presented by the anticipated rise in the full-year dividend to sell its holding,” Messrs. Burns and Hardie said in their report.

They noted that Ben van Beurden, who began as chief executive of Shell at the start of the month, is unlikely to be wed to the company’s ownership of the Woodside stake, which would make a decision to sell easier for him to make.

And if Shell is valuing Woodside in U.S. dollar terms, that won’t be helped by the strengthening of the greenback even as the Australian government and central bank remain keen for the Aussie to go lower, the analysts said.

At the same time the sale of the Woodside stake is a relatively fast and simple divestment option for Shell, which is most likely to seek to offload the shares in one hit and probably would turn to a range of institutional investors globally, Messrs Burns and Hardie said.

A spokesman for Shell declined to comment on the company’s plans for its Woodside stake.

Woodside’s shares are currently trading at about A$38.90, having recovered from an initially weak start to 2014. That’s still shy of the A$42.23 that Shell sold a basket of shares at in 2011, but well above the A$14.20 in cash it was offering when its takeover attempt was thwarted almost 13 years ago.